A multiple chamber type semiconductor manufacturing system constructed as shown in FIG. 1 includes a transfer chamber 1 around which a plurality of process chambers stations 2a, 2b. 2c, 2d, 2e, each comprising a process chamber, and a workpiece delivery station 3 for delivering workpieces to and from the outside are arranged. The inside of the transfer chamber 1 is normally held in vacuum by suitable vacuum equipment.
The transfer chamber 1 is constructed as shown in FIG. 2, having a handling robot A disposed rotatably in its central region. Constituting its peripheral wall, partition walls 5 that are opposed to the process chamber stations 2a, 2b, 2c, 2d, 2e and the workpiece delivery station 3 are formed with gates 6, respectively, each of which provides an inlet and outlet for a workpiece into and out of each process chamber station. These gates 6 so as they may be opened and closed are provided with their respective opening/closing doors (not shown) arranged in opposition thereto, respectively, inside the transfer chamber 2.
For the handling robot A is used typically a robot of double arm type, so called "frog leg" type, which is constructed as shown in FIG. 3 through FIGS. 6A and 6B.
As shown, the handling robot A has a pair of arms 7a and 7b of an identical length each of which is turnable about a center of rotation. It also has a pair of carrier tables 8a and 8b of an identical form, having their respective bases to each of which respective one ends of a pair of links 9a and 9b having an identical length are connected. The respective one ends of the two links 9a and 9b are connected to each of the two carrier tables 8a and 8b through a frog leg type carrier table posture (attitude) control mechanism so that the two links may turn completely symmetrically with respect to each of the carrier tables 8a and 8b. And, one of the two links connected to each of the carrier tables 8a and 8b is connected to one of the arms while the other link is connected to the other arm.
FIGS. 4A and 4B show different forms of the frog leg type carrier table posture control mechanism mentioned above. Thus, as shown in FIG. 4A, the respective one ends of the two links 9a and 9b may be connected to each of the carrier tables 8a and 8b through a gear structure comprising a pair of gears 9c and 9c in mesh with each other so that the respective posture angles .theta.R and .theta.L of the links 9a and 9b with respect to each of the carrier tables 8a and 8b may always be held identical to each other. This permits each of the carrier tables 8a and 8b to be oriented and to be moved in a radial direction of the transfer chamber 1. For the links 9a and 9b to be connected to the carrier tables 8a and 8b, in lieu of the gears a crossed belting arrangement 9d may be employed as shown in FIG. 4B.
FIG. 5 shows a conventional mechanism for turning the arms 7a and 7b independently of each other. The bases of the arms 7a and 7b are each in the form of a ring and are constituted with ring bosses 10a and 10b, respectively, which are positioned coaxially about the center of rotation and supported turnably with respect to the transfer chamber 1.
Inside of each of the ring bosses 10a and 10b is arranged arranged a disk boss 11a, 11b coaxially therewith and opposed thereto, respectively. Each pair of the ring boss and the disk boss 10a and 11a, 10b and 11b that are opposed to each other are magnetically coupled together with each of a magnetic coupling 12a, 12b in the rotary direction.
The rotary shafts 13a and 13b of the disk bosses 11a and 11b are arranged coaxially with each other and are connected to the output sections of the motor units 14a and 14b, respectively, which are in turn supported coaxially with each other and axially deviated in position from one to the other on a frame 1a of the transfer chamber 1. Here, the rotary shaft 13b of one motor unit 14b is elongated and arranged to pass through the other motor unit 14a and then to continue to extend upwards.
The motor units 14a and 14b may each be an integral combination of an AC servo motor 15 and a reducer 16 using a harmonic drive (a trade name, the representation which will not be repeated hereafter) in which the output sections of the reducers 16 and 16 are connected to the base ends of the rotary shafts 13a and 13b, respectively. Because once the arms 7a and 7b are positioned the transfer chamber 1 is to be maintained in a vacuum state, partition wall 17 is provided between the ring bosses 10a, 11b and the disk bosses 11a,11b.
FIGS. 6A and 6B are used to describe an operation of the handling robot A. When the two arms 7a and 7b lie at diametrically opposed, symmetrical positions about the center of rotation as shown in FIG. 6A, the two links 9a and 9b will each have had turned to have its two legs opened at maximum with respect to the carrier tables 8a and 8b. The two carrier tables 8a and 8b will then have been moved towards the center of rotation or turning.
In this state, turning the two arms 7a and 7b in a given direction will cause the two carrier tables 8a and 8b to turn about the center of rotation while maintaining their radial positions. Conversely, turning the two arms 7a and 7b from the state shown in FIG. 6A in opposite directions such as to have them approach each other will cause the one carrier table 8a of the position where the angle the arm 7a makes with the arm 7b is decreasing to be pushed by the links 9a and 9b to move to project radially outwards and thus to be plunged or forced into the process chamber of the one of stations 2a, 2b, 2c, 2d and 2e that is adjacent thereto radially outside of the transfer chamber 1 as shown in FIG. 6B.
In this case, while the other carrier table is moved towards the center of rotation or turning, the distance of this movement will be small because of the angles the arms 7a and 7b are making with the links 9a and 9b.
In the conventional handling robot described, a plurality of coaxial drive shafts must be provided and a motor unit is combined with a load by using, for example, a hollow shaft, as shown in FIG. 5. For these reasons, an elongated path of power transmission is entailed. There may thus result a positioning inaccuracy and a twisting that tend to produce vibrations. In order to avoid these inconveniences, it is desirable to shorten the path of power transmission as much as possible.
As a related prior art, there also exists a handling robot that makes use of a direct drive type motor operated in a vacuum as shown in Japanese Patent Literature No. Hei 8-506771 A in which a pair of motors are arranged coaxially and vertically up and down with their output shafts oriented in a same direction. The upper motor is hollow into which the output shaft of the lower motor is inserted. Thus, the output shaft of the lower motor is again necessarily elongated and also to that extent there may still arise a problem of twisting vibrations. A further problem involved in this type of the prior art is the need to use a special material that less emits gases for windings that constitute the motors, and such components and parts as sensors and bearings.
In an attempt to meet with these problems there has also be proposed as shown in Japanese Patent Literature No. Hei 7-55464 B a handling robot in which a pair of motors are arranged coaxially and vertically up and down with their output shafts opposed to each other. These opposed output shafts of the motors have a flange type driving member fastened thereto which is connected to a driven member with a magnetic coupling. In this prior art, the two motors are allowed to project both upwards and downwards and as a result the drive section including these motors is constructed to allow the axial center part to come to interfere with the handling operation part.
This requires the handling operation by the carrier tables to be performed radially outside of the drive section including the two motors, and thus the handling operation part to be larger in its radius of rotation, and hence involves the problem that the transfer chamber in which the handling operation part is accommodated must be larger in size.
The present invention has been created with the above mentioned problems taken into account and has for an object thereof to provide a handling robot that makes the output section of a motor unit extremely rigid, prevents positioning in a handling operation from becoming inaccurate and eliminates occurrence of vibrations due to a twisting deformation, and yet permits the presence of a drive section including a motor unit to hinder in no way an operation of the handling working section.